San Francisco police evacuated Jose Ortega Elementary School in the City's Lake Merced neighborhood after someone found a note about a bomb threat.
After a three-hour search turned up nothing, police allowed students and teachers back inside the school shortly before 11 a.m.
Police said the call came in at 8 a.m. Friday morning regarding a possible threat to the school at 400 Sargent St. The school district sent out an email saying "a note with a bomb threat was found."
Students would be allowed to return to class when there is an "all-clear," police said. Police on the scene said the threat did not seem credible.
Officers said Monday's threat comes about two weeks after another threat was made against Lowell High School, less than two miles away from Ortega.